Water as an Abiotic Factor Alexia Tanti Instructions
Water as an Abiotic Factor Alexia Tanti
Instructions Do not go through the PPT all at once but: First understand learn the terms (and their meanings) in the slide 3. Go through the slides 4 to 6, making sure you understand learn the terms (and their meanings) related to the water cycle. Further instructions on slide 7. Please note that the material covered in this material would take at least 2 weeks to cover at school (experiments apart), so don't expect to learn everything in 30 minutes just by watching the PPT once. You might consider making short notes as you go along.
Each living thing is adapted to the place where it lives - its environment The environment is effected by many Abiotic factors: non-living elements that effect the survival of an organism, e. g. water, light, temperature, soil type, nutrients, etc. study
Availability Of Water All organisms need water as most cellular reactions take place in the presence of water. Plants need water to produce their own food by photosynthesis: Carbon Dioxide + Water Sunlight & Chlorophyll Oxygen + Glucose Organisms living in dry places have adaptations that cut down on water loss, whereas animals living in rivers have to withstand the fast currents. Water is recycled through an ecosystem. The path that water takes through an ecosystem is called the Water Cycle. study
The Water Cycle The steps involved in the water cycle are: Evaporation: liquid water from the sea, lakes, rivers, etc…, and also from the surface of organisms turns into water vapour as it warms to boiling temperature. Condensation: warm air comes in contact with cold water, so water vapour turns into water droplets. Precipitation: water droplets fall to Earth as rain, snow, hail, dew, etc… Organisms take up water from the ground, e. g. plants for photosynthesis, animals to drink, etc… Aerobic Respiration in eukaryotic organisms releases water vapour into air Transpiration: some water taken up by plants, passes out of their leaves; Excretion: animals lose water to the air, through sweat or in their wastes products. Runoff: water from rain may fall onto roads, mountains or even soak into the soil. In time, this water flows into oceans, rivers, ponds or lakes where some of it evaporates into the air. Study meaning of terms
Instructions Go through the slides 8 to 14 to understand very well the complicated concept of Transpiration. Further instructions on slide 18. REMEMBER : the material covered in this material would take at least 2 weeks to cover at school (experiments apart), so don't expect to learn everything in 30 minutes just by watching the PPT once. You might consider making short notes as you go along.
TRANSPIRATION + Adaptation Of Plants To Reduce Water Loss Transpiration is the process by which water is forced up a plant from the soil through the stem, up to the leaves, and out to the atmosphere. study Passage of water from the roots to the leaf: To replace the water lost by evaporation, a plant takes up water from the soil through the roots. The flow of water through the plant is called the transpiration stream. Water is taken in from the soil via the roots. Roots have many tiny root hair cells that increase the amount of water the plant can absorb from the soil, as they which have a large surface area. Water is absorbed into the roots by osmosis. study
Water then moves into the root’s xylem and rises up the xylem vessels of the stem. Water manages to move up, against the force of gravity because of: a pushing force caused by the root pressure, since water is continuously entering the root (so since it has nowhere to go it pushes up into the root). the water’s power of cohesion (capillary action). Water molecules have the tendency to move up a narrow tube because they hold on to each other and to the sides of the tube. This helps to suck water up the plant. As water escapes out of the leaf during transpiration, more water moves up the xylem by a suction pressure (a pulling force). Watch
The Transpiration Stream Picture shows flow of water from when it enters the soil to when it leaves through the stomata. Note that some water is used by the leaf cells for photosynthesis. Make sure to understand the path taken by water
On the underside of the leaves are tiny holes called stomata. Picture showing stomata in bottom layer of cells inside the leaf Stomata are important as: they allow the plant to take in CO 2, needed for photosynthesis. (Meanwhile they also allow O 2 out of the leaf. ) they allow water to evaporate out of the leaf.
Plants control the amount of water lost through transpiration by opening and closing their stomata. Two guard cells surround each stoma. They can open and close the stoma by becoming more turgid or flaccid. Revise: Refer to “Biology for Life”, Pg 246, figure 6. Watch this video to see an explanation of how stomata open and close: https: //www. youtube. com/watch? v=JQvd. XX 7 h. Gq. I
Transpiration is important for the plant: to pull water up from the roots to the leaves, so they can do photosynthesis as water is pulled up the transpiration stream, it carries mineral salts with it as water evaporates, the plant cools down Open this link and watch the video https: //www. youtube. com/watch? v=Kv_0 udatlh 8 study
Instructions Go through the slides 15 to 18 to understand experiments on the rate of transpiration. Go through the slides 19 to 27 to understand what factors effect how much transpiration is done by a plant. It is very important that you can interpret graphs related to these factors. Further instructions on slide 28 REMEMBER : the material covered in this power point would take at least 2 week to cover at school (experiments apart), so don't expect to learn everything in 30 minutes just by watching the PPT once. You might consider making short notes as you go along.
Experiments To Measure The Rate Of Transpiration: A) Weighing method – using a MASS POTOMETER Method: A plant is uprooted and placed in a flask with water. Some oil is poured in the flask over the water. (Or else, the conical flask may be covered with a plastic bag. ) Precaution: to prevent any water from evaporating. The total mass is measured. The apparatus is left in a well-lit place and the mass is measured again after 1 hour. Conclusion: As water is lost from the leaves by transpiration, the mass of the apparatus decreases, so the rate of transpiration can be calculated as the mass lost per hour. To measure the rate of transpiration in different plants: use an identical set up with different plants of similar size and compare the amount of mass lost by each plant in a given amount of time
B) using a bubble POTOMETER Method: The roots of a plant are cut underwater. Precaution: so no air bubbles enter the xylem The shoot is inserted through the rubber bung of a water-filled potometer. All joints are sealed with Vaseline. Precaution: so the potometer is airtight Watch this video about hot to set up a potometer An air bubble is then inserted into the open end of the tube. This is done by: raising the potometer for a second above the water. allow a few water drops to fall out immerse in the water again. https: //www. youtube. com/watch? v=o. Ur 1 P 9 RZn. EU An air bubble should form between the water. The apparatus is placed in a well-lit place. The position of the air bubble is noted again after a given amount of time (e. g. 10 minutes).
Results: As transpiration takes place along the shoot, the air bubble moves along the potometer tube, towards the shoot. The rate of transpiration is calculated by measuring the distance moved by the air bubble in the allocated time. Rate of transpiration = distance moved by air bubble Time taken (for bubble to move that distance) Conclusion: The rate of transpiration calculated is equal to the rate of water uptake of the plant, which is assumed to be equal to the rate of water loss. To measure the rate of transpiration in different plants: use identical potometers with shoots taken from different plants. Make sure these shoots are of similar size and contain the same number of leaves. Also, place the potometers in the same environmental conditions. Then work out the rate of transpiration for each shoot.
Different types of BUBBLE potometers reservoir Air bubble Calibrated capillary tube water beaker Note: the reservoir helps to reset the bubble as it allows the air bubble to travel back to the start of the measuring scale when the experiment is repeated
Factors effecting the Rate of transpiration: Factor Description of rate Explanation In bright light, transpiration increases _________ In the presence of light the stomata open wider to allow more carbon dioxide into the leaf for photosynthesis. As a result more water is lost. At higher temperatures, transpiration increases _________ At higher temperatures, water warms up quickly and so evaporates of water takes place more quickly. In windy conditions, transpiration increases _________ Water vapour is quickly removed by air movement, so diffusion of water vapour out of the leaf is speeded up. In humid conditions, transpiration _________ decreases If the leaf is already surrounded by moist air, diffusion of water vapour out of the leaf decreases (low conc. gradient). Light Temperature Wind (moving air) Humidity Understand study well
Factors effecting the Rate of transpiration: Understand well This graph shows how the rate of transpiration changes as each abiotic factor listed increases
Stomata are open during the day - Stomata close during the night - to allow carbon dioxide to enter the leaf for photosynthesis when no carbon dioxide is needed. Since most water vapour is lost through the stomata… rate of transpiration decreases at night. Observations from graph: 1. as transpiration rate increases, stomatal aperture (how much a stoma is open, and how many stomata are open) increases. 2. In moving air (windy), rate of transpiration keeps increasing at a fast rate, while in still air (no wind), rate of transpiration increases at a much slower rate
Experiments to show the factors that affect the rate of transpiration A potometer is used to investigate how the rate of transpiration changes in different conditions. In order to get good results, it is important to change just one condition (variable) at a time. q To investigate the effect of temperature on the rate of transpiration: Put a number of identical potometers containing a shoot from the same type of plant, with the same number of leaves, at different temperatures. It should be observed that as temperature increases, rate of transpiration increases. q To investigate the effect of humidity on the rate of transpiration: Take two identical potometers and put a shoot from the same type of plant, with the same number of leaves in each. Cover one of the shoots with a plastic bag, so humidity will form around the leaves (as water lost by transpiration is trapped in the bag). As humidity increases the rate of transpiration will decrease.
increasing Line graph is showing that rate of transpiration was high when humidity was low, and is decreasing as humidity is increasing
Experiments to show the factors that affect the rate of transpiration q To investigate the effect of wind air currents on the rate of transpiration: Put two identical potometers containing a shoot from the same type of plant, with the same number of leaves, at the same temperature. If a fan is placed in front of one of the shoots, it will be observed that rate of transpiration increasers in the presence of air currents (wind) (contd) Observations from graph: 1. as wind speed increases, transpiration increases. 2. However, at a certain point, transpiration starts to decrease due to some other abiotic factor, e. g. water that is not available anymore
Watch the linked video. It shows how a potometer is set up and also how to investigate the effect of air currents on the rate of transpiration. https: //www. youtube. com/watch? v=g. Xoc. ZZDDPaw
Experiments to show the factors that affect the rate of transpiration (contd) q To investigate the effect of light on the rate of transpiration: Put a number of identical potometers containing a shoot from the same type of plant, with the same number of leaves, in different light intensities. It should be observed that as light intensity is increased the rate of transpiration increases. Precaution: In this experiment, it is important to place a heat shield (glass container filled with water) between the plants and the light source. So, any heat generated by the light source does not reach the plant. This avoids creating another variable. Identical set ups to investigate how different abiotic factors effect transpiration. Heat shield
Experiments to show the factors that affect the rate of transpiration (contd) q To investigate the effect of cuticle thickness on the rate of transpiration: Two identical potometers are set up with two different plants whose leaves have cuticles of different thickness It will be found that the thicker the cuticle, the slower the rate of transpiration. This is so, because evaporation of water is slowed down (as the distance that water molecules need to travel to reach the atmosphere is longer). Note: Ø Plants having a smaller number of stomata on their leaves, have a slower rate of transpiration than plants with a large number of stomata.
Instructions Go through the slides 29 to 32 to understand how different factors affect the rate of transpiration. Further instructions on slide 33. REMEMBER : the material covered in this powerpoint would take at least 2 weeks lessons to cover at school. So don't expect to learn everything in 30 minutes just by watching the PPT once. You might consider making short notes as you go along.
Adaptations of plants to control the rate of transpiration: If water evaporates from a plant faster than it can be replaced from the soil, the cells lose their turgidity and the plant wilts (stem bends), and may even die. The main weather conditions in which plants wilt are: Hot, dry weather: when evaporative power of the atmosphere is great and the rate of transpiration is high. very cold weather: when the soil freezes, so water cannot be taken up by roots.
Plants have different adaptations to control the amount of water lost by transpiration: Leaf fall – deciduous trees shed their leaves during winter to reduce water loss by transpiration during the cold months when water in the soil may freeze. Number and position of stomata – to reduce transpiration: less stomata should be present. the largest number of stomata is on the lower side of the leaves, away from direct sunlight stomata may be sunk deep down into pits of the epidermis. Leaf shape – the smaller the surface area, the less the rate of transpiration. Some plants keep their leaves folded or rolled up. Other plants, have their leaves reduced to spikes. Succulent tissues - Some plants, e. g. cacti, have a storage of water in their tissues. Leaf cuticle - The waxy cuticle above the epidermis also reduces transpiration. Root types – Plants living in dry places, may have: shallow roots to collect the occasional rainfall, deep roots to absorb water from deep down into the soil. View PPT about stomata distribution
Experiment to compare transpiration from each side of a leaf: Method: A piece of anhydrous cobalt chloride paper is attached on each side of a leaf and held in place for a given time. N. B. Anhydrous cobalt chloride paper is blue and goes pink in the presence of water. Result: The cobalt chloride paper that goes pink first shows that side of the leaf loses water more rapidly than the other. This will be the side containing the largest number of stomata, through which water will be evaporating. Conclusion: In most plants, the Anhydrous copper cobalt paper from the underneath of the leaf will be more pink than the paper from the surface, because the underside of the leaf has more stomata, meaning that more water evaporates from this part of the leaf. View video explaining such an experiment on link: https: //www. youtube. com /watch? v=nb GWVy. Bv 7 K 0
Instruction The last three slides are on osmoregulation. This is a homeostatic process on how water is controlled in protists and mammals.
Osmoregulation is the process by which the concentrations of water and salts in the body are kept constant study Water loss is a major concern for all organisms as they all need a stable internal environment for their cell/s to function properly. So, all organisms have special adaptations for minimizing water loss. Unicellular Protists, such as Amoeba and Euglena carry out osmoregulation by means of the Contractile Vacuole. The concentration of water in the cytoplasm must be constantly in equilibrium with that of the surrounding waters. As they live in fresh water, water outside their body is more dilute than the cytoplasm. So, water enters the cell, through the semi-permeable cell membrane by osmosis. Any extra water that the cell does not need goes into the contractile vacuole. As it fills up with water, it enlarges and moves towards the cell membrane. There it bursts, emptying the excess water out of the cell. This process is repeated over and over again
Osmoregulation in Amoeba Try to learn how to draw Amoeba doing osmoregulation
Mammals control the amount of water in the body by the kidneys, through the amount of urine produced. If the concentration of water in the blood falls, the kidneys reduce the amount of water excreted, so a small volume of very concentrated urine is produced to reduce water loss. If the concentration of water in the blood increases, the kidneys do not reabsorb much water into the blood, and produce a large volume of very dilute urine. This increases the amount of water lost during excretion.
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